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Senior Frontend Interview Questions

Some questions about frontend development that might be in your next job interview. The questions were formulated by @mauvieira, a super senior fullstack developer

General Frontend

What are the strategies we can use to optimize the performance of web applications?
- CDNs, GraphQL (maybe) to reduce overfetching, improve backend performance, use SSR and/or SSG, lazy loading for loading assets only when it's needed, minimize and compress HTML, CSS and JS files, and optimize images by compressing and resizing them.
What are Web Vitals (LCP, FID, CLS)? And how are they applied in the real world?

《JavaScript核心技术开发解密》

运行环境<执行上下文>：

-> 全局环境：代码运行首先进入全局环境，也是最外层的作用域

-> 函数环境：当函数被调用执行时创建的上下文环境，即函数作用域

-> eval环境：todo

html

行内元素：span，a；块级元素： div，h1。。。 p ul li
html语义化：正确的标签做正确的事情，页面内容结构清晰，利于seo，方便维护阅读理解
label标签：定义表单控件之间的关系，
iframe：优点：可以原封不动展示页面，方便做模版内容嵌入，做微服务，可以通过postMessage进行通信。缺点：滚动条，阻塞onload，无法检索，不利于seo，浏览器共享连接池，影响加载速度
h5中form关闭自动完成：autocomplete=off
！DOCTYPE：声明使用xhtml还是html，xhtml是xml重写的html，规范更严格
src和href区别：href用在link和a上，引用和页面关联，src表示引用资源，用资源替换当前元素，如img，video，script，iframe
dom tree构建过程：html解释器将网络或者本地磁盘获取的html网页和资源从字节流解释成dom树结构， java scrip执行在将字符串解释成词语创建各种节点的时候， html解释器加载文件流的时候会进行词法分析、语法分析，将词语转成节点后，多个节点形成的树状结构就是dom树。
img的title和alt：title是图片信息，alt是图片不显示时显示的文字

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Interview Questions

Node.js

Q1: What do you mean by Asynchronous API? ☆☆

Answer: All APIs of Node.js library are aynchronous that is non-blocking. It essentially means a Node.js based server never waits for a API to return data. Server moves to next API after calling it and a notification mechanism of Events of Node.js helps server to get response from the previous API call.

Source: tutorialspoint.com

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